TTbarWithJpsimumuFilter.cxx

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/*
  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
*/
#include "GeneratorFilters/TTbarWithJpsimumuFilter.h"
 
#include "GaudiKernel/MsgStream.h"
#include "TruthUtils/MagicNumbers.h"
 
//--------------------------------------------------------------------------
TTbarWithJpsimumuFilter::TTbarWithJpsimumuFilter(const std::string& fname,
        ISvcLocator* pSvcLocator)
    : GenFilter(fname,pSvcLocator)
 
{
    declareProperty("SelectJpsi",m_selectJpsi=true);
    declareProperty("JpsipTMinCut",m_JpsiPtMinCut=0.); 
    declareProperty("JpsietaMaxCut",m_JpsiEtaMaxCut=5.);
}
 
//--------------------------------------------------------------------------
TTbarWithJpsimumuFilter::~TTbarWithJpsimumuFilter() {
}
 
//---------------------------------------------------------------------------
StatusCode TTbarWithJpsimumuFilter::filterInitialize() {
    ATH_MSG_INFO("Initialized");
    return StatusCode::SUCCESS;
}
 
//---------------------------------------------------------------------------
StatusCode TTbarWithJpsimumuFilter::filterFinalize() {
    ATH_MSG_INFO(" Events out of " << m_nPass+m_nFail << " passed the filter");
    return StatusCode::SUCCESS;
}
 
 
//---------------------------------------------------------------------------
StatusCode TTbarWithJpsimumuFilter::filterEvent() {
    //---------------------------------------------------------------------------
 
    bool pass = false;
    bool isjpsi = false;
 
    for (const HepMC::GenEvent* genEvt : *events_const()) {
 
        // Loop over all truth particles in the event
        // ===========================================
        for(const auto& part: *genEvt) {
            if (std::abs(part->pdg_id())!=443) continue;
            if (HepMC::is_simulation_particle(part)) continue;
            if(!isLeptonDecay(part,13)) continue;
            if ( !passJpsiSelection(part) ) continue;
            isjpsi=true;
        } 
 
    } // loop on events (only one at evgen - no PU)
 
    if (m_selectJpsi && isjpsi) pass = true;
    
    setFilterPassed(pass);
    return StatusCode::SUCCESS;
}
 
// ========================================================
bool TTbarWithJpsimumuFilter::isLeptonDecay(const HepMC::ConstGenParticlePtr& part, int type) const {
    auto end = part->end_vertex();
    if(!end) return true;
#ifdef HEPMC3
    for (const auto& p: end->particles_out()) {
        if (std::abs(p->pdg_id()) !=  type ) return false;
    }
#else
    HepMC::GenVertex::particle_iterator firstChild = end->particles_begin(HepMC::children);
    HepMC::GenVertex::particle_iterator endChild = end->particles_end(HepMC::children);
    for(; firstChild!=endChild; ++firstChild) {
        int childtype = std::abs((*firstChild)->pdg_id());
        if( childtype != type ) {
            return false;
        }
    }
#endif
    return true;
}
 
// ========================================================
bool TTbarWithJpsimumuFilter::passJpsiSelection(const HepMC::ConstGenParticlePtr& part) const {
 
    const HepMC::FourVector& p4 = part->momentum();
    double pt = p4.perp();
    double eta = std::abs(p4.eta());
 
    if (pt < m_JpsiPtMinCut) return false;
    if (eta > m_JpsiEtaMaxCut) return false;
 
    return true;
 
}